Squamous cell carcinoma in the orbit of a dog

By Emma Scurrell

A nine-year-old male Rottweiler presented with unilateral exophthalmos and clinical findings revealed a retrobulbar mass. Fine needle aspirates were taken from the mass and the results are shown below.

Fig 1.The smears are highly cellular and the cell population is well-preserved (modified Wrights-Giemsa, x40).

Fig 2. The dominant cell population consists of neoplastic squamous epithelial cells present singly and in small clusters. There is associated neutrophilic inflammation present (x200).

Final Diagnosis

Squamous cell carcinoma (SCC)

Discussion

Squamous cell carcinomas are malignant, locally invasive neoplasms. The orbit would be a very unusual site for a primary SCC. A more common scenario is invasion of a primary sinonasal SCC through the medial orbital wall. Metastasis to the orbit from a primary SCC elsewhere is another possibility, but this is considered rare.